Containment Procedure: Direct interaction with SCP-691 in any form is strictly prohibited. It is to be considered armed and extremely dangerous at all times. Normal Euclid-class containment procedures apply.

Description: The true appearance and nature of SCP-691 is yet unknown, as anyone who views or listens to it becomes convinced they are seeing and hearing themselves. Up to 10 subjects, when simultaneously shown a live video feed of SCP-691's cell, insisted they saw and heard themselves within the cell, pleading for release and understanding. The same effect has been found in both digital and film photographs, with all who review the media claiming to see picture after picture of themselves, including [DATA EXPUNGED]. How SCP-691 produces this effect is unknown, as all forms of observation by humans seem to show oneself in all cases. According to remote scanning and observation, SCP-691 appears to have none of the same physiological makeup and nutritional needs as a regular human being. While in containment, SCP-691 demonstrates a cooperative and likable, if somewhat pathetic, persona. It does this to incite pity and empathy from its captors. However, any person who comes in contact with SCP-691 is immediately assaulted and strangled, presumably by the visage of oneself.

Addendum A: SCP-691 has breached its containment only once, having been let out by a confused member of security who, unaware of SCP-691's nature, was promptly strangled. During this breach, SCP-691 revealed itself to be highly predatory, evading capture for many hours by hiding in shadows and appearing to fully-armored security forces as one of their own, systematically leading them astray before killing them. The breach was finally contained when ████ tranquilized SCP-691. An interview transcript follows.

Dr. ██: Tell us what happened down there.

████ : Sure. I, uh… when I heard there was a containment breach, I went down to help. It was way too quiet down there. The red alarm lights were flashing, but besides that it was too dark to see anything, really. While walking down a corridor, I thought I heard a noise so I checked it out. That's… that's when I found myself hunched over a body on the ground. I mean, it wasn't me, but it was. It still had its fucking hands.. my hands… around the guy's throat when I found it, though he was clearly dead already. It looked up at me, with my own eyes, and screamed at me with my own voice. No words, just… It tried to rush me. But I had my (tranquilizer) gun out and got it before it got me. It's that simple.

Dr. ██: Were you afraid?

████ : …Yeah. You never do get used to seeing yourself in that fuckin' thing all the time. And it's always begging to be let out, crying and pleading, telling everybody there's been a mistake, that it has whatever family whoever it's talking to has. It tries to convince you it's the real you, that you're the fuckin' doppleganger. I guess everyone working at ████ has to face that. I can't even look in the mirror anymore, I always think I'm gonna see those eyes again. My eyes, but… but not. God damn that thing. God damn it. No more questions, please.

Addendum B: Permission to destroy SCP-691 has been denied by ████. Additional requests for destruction of SCP-691 will not be reviewed.